Stretchable Multi-Layer Film, Method of Formation and Application, and Articles Therefrom

ABSTRACT

Multi-layer films of the invention comprise sequential layers as follows: a topcoat layer; a boundary layer; a carrier layer; and an adhesive layer. Inclusion of the boundary layer between the topcoat layer and the carrier layer was, surprisingly, found to provide a multi-layer film that is more resistant to formation therein of compromising defects during intensified stretching when applying the film to a surface. Advantageously, the boundary layer generally promotes stretchability of the multi-layer film. Articles comprising the same and methods for their formation and use are also described herein.

BACKGROUND OF THE INVENTION

The present invention relates generally to multi-layer films useful forcovering surfaces, methods of making and using the same, and articlescomprising applied films of the invention.

A variety of paint protection films, paint film appliques, and othermulti-layer films are known. Many of those are based on one or morepolyurethane layers. Polyurethane chemistries generally provide one ormore properties including the following: environmental resistance,chemical resistance, abrasion resistance, scratch resistance, opticaltransparency, and other often desirable properties.

Attempts have been made to combine polyurethane layers with other layersof material in the form of a multi-layer film in order to improveproperties of the individual layers, such as gloss retention andenvironmental resistance. In some cases, an exterior (or topcoat) layeris applied to a polyurethane carrier layer in order to impart suchimproved properties. The inclusion of additional layers of materialwithin a multi-layer film can negatively impact other properties,however; for example, flexibility of the multi-layer film generallydecreases as more and thicker layers of material are included inmulti-layer film constructions. Decreased flexibility can not only makeit more difficult to adequately conform the multi-layer film foradequate adherence to contoured surfaces, but it can also lead topremature edge lift of the multi-layer film during use. In addition,inadequate compatibility between adjacent layers can lead to potentialinterlayer delamination within such multi-layer films.

Several multi-layer films are readily available on the market today foruse in paint protection. For example, Minnesota Mining & ManufacturingCo. (“3M”) in St. Paul, Minn., markets polyurethane-based sheet “PaintProtection Film” under the SCOTCHGARD and VENTURESHIELD product lines.PCT Patent Publication No. WO 02/28636 describes a finishing filmcomprising a flexible polymeric sheet material having a first majorsurface and a second major surface and a pressure sensitive adhesivelayer covering at least a portion of the first major surface of thesheet material. The finishing film is described as being commerciallyavailable from 3M Co. under the trade designation, SCOTCHCAL PAINTPROTECTION FILM PUL 0612, and comprising a 6-mil polymer film comprisingan aliphatic polycaprolactone-based thermoplastic urethane elastomer.Examples of methods for formation of the polymer film described thereinare extrusion, calendaring, wet casting, and the like. Thereafter, awaterborne polyurethane coating is formed on one side of the polymerfilm, with the other side of the polymer film being laminated to anacrylic pressure sensitive adhesive.

PCT Patent Publication No. WO 03/002680 describes an adhesive sheetcomprising a flexible base material, an adhesive layer disposed on aback surface of said base material, and a protective layer disposed on afront surface of the base material. The protective layer described inPCT Patent Publication No. WO 03/002680 is made of a hydrophilic filmcontaining a curing resin and a hydrophilic agent of an inorganic oxide.The base material contains a layer of a first polyurethane resin that isa reaction product of polyester polyol and a polyfunctional isocyanatecompound. Preferably, the base material comprises a lower layercontaining the first polyurethane resin and an upper layer disposedbetween the lower layer and the protective layer that adheres to theprotective layer and contains a second polyurethane resin that is areaction product of a polycarbonate polyol and a polyfunctionalisocyanate compound. The upper layer preferably comprises a hardpolyurethane resin in comparison with the first polyurethane resin ofthe lower layer to enable adhesion between the entire base material andthe protective layer to be effectively increased through the upperlayer, even if the film of the protective layer is comparatively hardand has a low-temperature elongation, differing to a large extent fromthat of the lower layer of the base material. The polyester polyolforming the first polyurethane resin may be formed from a diol havingcaprolactonediol in the main chain.

U.S. Pat. No. 8,765,263 describes a multilayer protective filmcomprising a first layer, a second layer, and a pressure sensitiveadhesive (PSA) layer. The first layer at least comprises apolyester-based polyurethane, a polycarbonate-based polyurethane, or acombination or blend of both. The second layer at least comprises apolycaprolactone-based thermoplastic polyurethane. One major surface ofthe first layer is bonded to one major surface of the second layer, andthe PSA layer is bonded to an opposite major surface of the second layersuch that the second layer is sandwiched between the first layer and thePSA layer. The predominant method of forming the second layer isdescribed as extruding the polycaprolactone-based thermoplasticpolyurethane at an elevated temperature through a die, although castingand injection molding are also described.

Typical during installation of such films is the need to stretch thefilm to adequately conform to non-planar substrates. When installed onhoods of automobiles, for example, film is often stretched about 10% toa stretched length of about 110%. To assist in stretchability of suchfilms, the film is often heated. In practice, however, amount of stretchis often inconsistent throughout a film. For example, when the film istacked (e.g., adhered to a substrate) too close to the portion of thefilm being stretched over adjacent portions of the substrate, stretch isoften intensified in that portion of film. As another example, when thefilm is not heated uniformly over the area where it is stretched,stretch is often intensified in those portions of the film beingstretched at a lower temperature. As a result, some portions of the filmare subjected to stretch of at least about 20% or more, while stretch inother areas is much less. Problematic, however, is the fact thatlocalized stretch to amounts as high as about 50% is not uncommon.

When film is stretched during the installation process, particularly tosuch a large degree in localized areas, properties of the films areoften compromised. Defects such as cracks, which extend longitudinallythrough a portion of the film's thickness, and, to a greater degree,splits, which extend longitudinally through the film's entire thickness,are often present in such films as evidence of their compromisedproperties. Given that installers of such film cannot always be reliedupon to following installation instructions and take precautions inminimizing intensified stretch across all portions of the film beinginstalled, film with properties more resistant to being compromisedduring intensified stretching are desirable.

SUMMARY OF THE INVENTION

Multi-layer films of the invention comprise sequential layers asfollows: a topcoat layer; a boundary layer; a carrier layer; and anadhesive layer. Inclusion of the boundary layer was, surprisingly, foundto provide a multi-layer film that is more resistant to formationtherein of compromising defects during intensified stretching whenapplying the film to a surface. Advantageously, the boundary layergenerally promotes stretchability of the multi-layer film. Articlescomprising the same and methods for their formation and use are alsodescribed herein.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS

FIG. 1A is a black-and-white photograph of a SEM image of themulti-layer film of Example 1 after being stretched 30%.

FIG. 1B is a black-and-white photograph of a SEM image of themulti-layer film of Example 1 after being stretched 60%.

FIG. 2A, which is prior art, is a black-and-white photograph of a SEMimage of the multi-layer film of Comparative Example C1 after beingstretched 30%.

FIG. 2B, which is prior art, is a black-and-white photograph of a SEMimage of the multi-layer film of Comparative Example C1 after beingstretched 60%.

FIG. 3A, which is prior art, is a black-and-white photograph of a SEMimage of the multi-layer film of Comparative Example C2 after beingstretched 30%.

FIG. 3B, which is prior art, is a black-and-white photograph of a SEMimage of the multi-layer film of Comparative Example C2 after beingstretched 60%.

FIG. 4A, which is prior art, is a black-and-white photograph of a SEMimage of the multi-layer film of Comparative Example C3 after beingstretched 30%.

FIG. 4B, which is prior art, is a black-and-white photograph of a SEMimage of the multi-layer film of Comparative Example C3 after beingstretched 60%.

DETAILED DESCRIPTION OF THE INVENTION

Multi-layer films of the invention comprise at least a carrier layerinterposed between an outwardly exposed topcoat layer and an outwardlyexposed adhesive layer. Further, the multi-layer film also comprises aninternal boundary layer. Preferably, the boundary layer is immediatelyadjacent to and interposed between the outwardly exposed topcoat layerand the internal carrier layer.

The boundary layer and the internal carrier layer are distinguishablebased on their relative moduli and thicknesses. Relative moduliaccording to the invention refers to relative values of the secantmodulus of the layer of material. Secant modulus is understood to be thevalue of stress divided by strain at a given value of stress or strainand is often referred to as the stress-strain ratio. For purposes ofthis invention when determining relative moduli, the secant modulus isevaluated for the layer at an elongation of 10% (also referred to as theM10 modulus). A DMA Q800 available from TA Instruments (New Castle,Del.) can be used to determine the relative moduli, evaluating sampleseach having a size of 4-8 millimeters wide, 0.02-0.04 millimeter thick,and 5-12 millimeters long at a stress ramp rate of 18 MPa per minute tofailure (or machine limits). Moduli can also be determined by testingaccording to ISO 527-2 or ASTM D-412 test methods. The M10 modulus for alayer is calculated by dividing the stress at 10% elongation by 0.1(strain=10%).

In general, the M10 modulus of boundary layers of the invention isgreater than the M10 modulus of the internal carrier layer. In oneembodiment, the M10 modulus of the boundary layer is at least about 20%greater than the M10 modulus of the carrier layer. In a furtherembodiment, the M10 modulus of the boundary layer is at least about 50%greater than the M10 modulus of the carrier layer. In yet a furtherembodiment, the M10 modulus of the boundary layer is at least about 75%greater than the M10 modulus of the carrier layer. In yet a furtherembodiment still, the M10 modulus of the boundary layer is at leastabout 100% greater than the M10 modulus of the carrier layer.

In another embodiment, the M10 modulus of the boundary layer is at leastabout 20% greater than the M10 modulus of the carrier layer and at leastabout 20% greater than the M10 modulus of the topcoat layer sandwichingthe boundary layer. In a further embodiment, the M10 modulus of theboundary layer is at least about 50% greater than the M10 modulus of thecarrier layer and the M10 modulus of the topcoat layer. In yet a furtherembodiment, the M10 modulus of the boundary layer is at least about 75%greater than the M10 modulus of the carrier layer and the M10 modulus ofthe topcoat layer. In yet a further embodiment still, the M10 modulus ofthe boundary layer is at least about 100% greater than the M10 modulusof the carrier layer and the M10 modulus of the topcoat layer.

The boundary layer generally promotes stretchability of the multi-layerfilm. In one embodiment, the boundary layer has an ultimate elongationthat is greater than that of the topcoat layer. In a further embodiment,ultimate elongation of the boundary layer is at least about 25% greaterthan ultimate elongation of the topcoat layer. In yet a furtherembodiment, ultimate elongation of the boundary layer is at least about50% greater than ultimate elongation of the topcoat layer. In still yeta further embodiment, ultimate elongation of the boundary layer is atleast about 100% greater than ultimate elongation of the topcoat layer.

To offset the increased overall stiffness arising from inclusion of therelatively high modulus boundary layer—as compared to modulus of thecarrier layer—in the multi-layer film, it has been found beneficial touse a lower modulus carrier layer than is typically used in manymulti-layer films consisting of a topcoat layer, carrier layer, andadhesive layer, for example. In one embodiment, the M10 modulus of thecarrier layer is less than about 20 MPa at 25° C. In another embodiment,the M10 modulus of the carrier layer is less than about 15 MPa at 25° C.

The secant modulus can also be evaluated for a layer at an elongation of100% (also referred to as the M100 modulus), whereby the M100 modulusfor the layer is then equal to the stress at 100% elongation. In oneembodiment, the M100 modulus of the carrier layer is less than about 5MPa at 25° C. In another embodiment, the M100 modulus of the carrierlayer is less than about 4 MPa at 25° C.

In one embodiment, modulus of the boundary layer decreases at a slowerrate as temperature is increased as compared to behavior exhibited bythe carrier layer when similarly tested. In another embodiment, modulusof the boundary layer decreases at a slower rate as temperature isincreased as compared to behavior exhibited by the topcoat layer whensimilarly tested. In a further embodiment, modulus of the boundary layerdecreases at a slower rate as temperature is increased as compared tobehavior exhibited by both the carrier layer and the topcoat layer whensimilarly tested. For example, M100 modulus of the boundary layer at 60°C. is at least about 60% of the M100 modulus of that boundary layer at25° C. in one embodiment. In another embodiment, M100 modulus of theboundary layer at 60° C. is at least about 70% of the M100 modulus ofthat boundary layer at 25° C. To determine moduli values for purposes ofthis analysis, a DMA Q800 available from TA Instruments (New Castle,Del.) can be used to determine the moduli, evaluating samples eachhaving a size of 4-8 millimeters wide, 0.02-0.04 millimeter thick, and5-12 millimeters long in tension mode at a frequency of 1 Hz, a strainof 0.3%, and a temperature ramp rate of 3° C./minute to failure (ormachine limits). Moduli can also be determined by testing according toISO 527-2 or ASTM D-412 test methods.

As compared to the internal carrier layer, the boundary layer has athickness that is less than about 50% of thickness of the carrier layer.In a preferred embodiment, the boundary layer's thickness is less thanabout 20% of thickness of the carrier layer.

Unexpectedly, use of such a boundary layer within (and interior to) amulti-layer film facilitates obtainment of superior stretchability ofthe multi-layer film without compromised integrity. Compromisedintegrity is evidenced by, for example, cracking, splitting, and thelike of the multi-layer film upon stretching. While the carrier layer inthis further embodiment can be extruded or in-situ polymerized, asdescribed in more detail below, preferably it is in-situ polymerized.

Carrier Layer

The term “carrier layer” is used herein to refer to the layer(s)interposed between the outwardly exposed topcoat layer and the outwardlyexposed adhesive layer. In certain contexts, a carrier layer may also bereferred to as a “base layer” or a similar designation. In general, thecarrier layer of multi-layer films of the invention is referred to as a“mid-ply layer” when it contains multiple layers (i.e., “n” number ofindividual layers). However, the carrier layer of multi-layer films ofthe invention can be a single film layer according to other embodimentsof the invention. When multiple layers form the carrier layer, each ofthe “n” individual layers can be the same or different chemistries. Inan exemplary embodiment, each of the “n” individual layers hasessentially the same chemistry.

In an exemplary embodiment, carrier layers used in multi-layer films ofthe invention are polyurethane-based. For simplicity, the term“polyurethane” as used herein includes polymers containing urethane(also known as carbamate) linkages, urea linkages, or combinationsthereof (i.e., in the case of poly(urethane-urea)s). Thus,polyurethane-based carrier layers contain at least urethane linkages,urea linkages, or combinations thereof. Furthermore, polyurethane-basedcarrier layers are based on polymers where the polymeric backbone has atleast 80% urethane and/or urea repeat linkages formed during thepolymerization process.

Polyurethane-based carrier layers are prepared according to methods ofthe invention by reacting components, which include at least oneisocyanate-reactive (e.g., hydroxy-functional, such as polyol) componentand at least one isocyanate-functional (e.g., polyisocyanate) component.For example, components of exemplary polymerizable compositions andwhich are useful in the formation of preferred polyurethane-basedcarrier layers according to methods of the invention are described inU.S. Patent Publication No. US-2011-0241261-A1, entitled “Methods forPolymerizing Films In-Situ Using a Radiation Source” and incorporatedherein by reference in its entirety. Such in-situ polymerized carrierlayers, which, as described in PCT Patent Application No. WO2017/156507, provide improvements to conventional protective sheets, arepreferably used as the carrier layer in multi-layer films of the presentinvention.

In exemplary embodiments, polymerization of the polymerizablecomposition is initiated using at least one radiation source selectedfrom ultraviolet radiation, thermal radiation, and electron beamradiation. Methods of the invention can utilize continuous processing orbatch processing. For example, continuous processing, such as web-basedpolymerization of the polyurethane-based carrier layer using relativelylow energy ultraviolet radiation, can be used in one embodiment of theinvention. As another example, batch processing, such as coating anultraviolet-curable composition on a discrete substrate and irradiatingthe same to form the polyurethane-based carrier layer can be used inanother embodiment of the invention.

According to a preferred aspect of methods of the invention, thepolymerizable composition for formation of the polyurethane-basedcarrier layer is essentially free of solvents. In addition to, forexample, environmental and safety concerns associated with solvent-basedprocessing, solvent-based processing typically entails use of elevatedtemperatures for effective removal of excess solvent from thepolymerized composition. It is preferred that polyurethane-based carrierlayers are essentially free of unreacted solvent. Thus, it is preferredthat the polymerizable compositions from which they are formed areessentially free of solvents.

Given its recognized beneficial properties, the carrier layer comprisesa polycaprolactone-based polyurethane according to an exemplaryembodiment of the invention. Any suitable polycaprolactone-basedpolyurethane can be used for the carrier layer, which is not limited tothose that are in-situ polymerized. For example, Schweitzer-MauduitInternational, Inc. (Greenfield, Mass.) supplies otherpolycaprolactone-based polyurethane films under the ArgoGuard™ 46510,ArgoGuard™ 49510, and ArgoGuard™ 49510-60DV trade designations.

Any suitable additives can be present in the carrier layer. Otheradditives are selected as known to those skilled in the art based on theintended application. Those skilled in the art are readily able todetermine the amount of such additives to use for the desired effect.

According to one embodiment of the invention, the carrier layer has athickness of about 5 microns to about 1,250 microns. Each of the “n”number of individual film layers therein can be as thin as about 5microns and up to about 50 microns in thickness, the presence of thickerlayers being particularly useful for ballistic applications. However, toimpart greater stretchability, a carrier layer having a thickness ofabout 220 microns or less is used according to one aspect of theinvention. According to further aspects, the carrier layer has athickness of about 180 microns or less. For example, the carrier layercan have a thickness of about 120 microns to about 180 microns. Not onlyis stretchability of the carrier layer, and hence overall multi-layerfilm, enhanced by using a thinner carrier layer, overall cost is reducedin this manner.

Topcoat Layer

In general, any outwardly exposed non-adhesive layer on a major planarside of the multi-layer film opposite the adhesive layer is referred toas the “topcoat layer.” Consistent with its name, the topcoat layer isan outwardly exposed, exterior layer of the multi-layer film as appliedto an article. Any suitable type of material can be used for the topcoatlayer in multi-layer films of the invention.

The topcoat layer can comprise any suitable chemistry. In general, thetopcoat layer provides one or more properties including the following:environmental resistance, chemical resistance, abrasion resistance,scratch resistance, optical transparency, and other often desirableproperties. According to an exemplary embodiment, the topcoat layer isnon-yellowing and exhibits gloss retention (e.g., maintaining of glosson the order of about 80 to about 90 gloss units). In an exemplaryembodiment, the topcoat layer comprises a polyurethane-based material.Many suitable topcoats are commercially available, including forexample, polyurethane coatings sold by PPG Aerospace PRC-DeSoto ofSylmar, Calif. under the Desothane™ HS trade designation (e.g.,Desothane™ HS CA8000).

In one embodiment, when present, the topcoat layer has a thickness ofabout 1 microns to about 28 microns. In a further embodiment, thetopcoat layer has a thickness of about 5 microns to about 20 microns. Instill a further embodiment, the topcoat layer has a thickness of about 5microns to about 15 microns. In yet a further embodiment, the topcoatlayer has a thickness of about 5 microns to about 12 microns. In yet afurther embodiment, the topcoat layer has a thickness of about 5 micronsto about 7 microns. However, the thickness of the topcoat layer can varysubstantially without departing from the spirit and scope of theinvention.

To protect the topcoat layer until application of the multi-layer filmto a substrate, a polymer liner (e.g., a clear polyester liner) or thelike may be positioned adjacent the topcoat layer such that the liner,as opposed to the topcoat layer, is temporarily outwardly exposed. Afterapplication of the multi-layer film to a substrate, such an optionalliner is generally removed for effective operation of the multi-layerfilm.

Boundary Layer

Interposed between the topcoat layer and the carrier layer is a boundarylayer according to the invention. Inclusion of the boundary layer was,surprisingly, found to provide a multi-layer film that is more resistantto formation therein of compromising defects during intensifiedstretching when applying the film to a surface. As discussed in thebackground herein, cracks and splits in the film often arise as evidenceof the film's compromised integrity after application to a surface. Thepropensity for such defects to arise in multi-layer films is increasedwhen utilizing a topcoat layer formulated to provide properties desiredfor many applications, which properties include the following:environmental resistance, chemical resistance, abrasion resistance,scratch resistance, and optical transparency.

The boundary layer is polymeric and can comprise as its base polymer apolycarbonate, a polyvinyl fluoride, a poly(meth)acrylate (e.g., apolyacrylate or a polymethacrylate), a polyurethane, modified (e.g.,hybrid) polymers thereof, or combinations thereof. In a preferredembodiment, the boundary layer is polyurethane-based. See U.S. Pat. No.4,476,293 for a description of exemplary polycarbonate-basedpolyurethanes useful for the boundary layer of the invention. Anysuitable additives can be present in conjunction with the base polymerin the boundary layer. Other additives are selected as known to thoseskilled in the art based on details of an intended application.

The boundary layer is of relatively high molecular weight, as evidencedby its melting point. That is, while the boundary layer can be formed byextrusion according to some embodiments of the invention, the boundarylayer is preferably of a sufficient molecular weight that extrusionthereof is not practical (i.e., if a polyurethane, the polyurethane isnot considered extrusion-grade polyurethane by those of ordinary skillin the art).

The boundary layer has any suitable thickness so as not to preventobtainment of desired properties associated with its stretchability. Inone embodiment, the boundary layer has a thickness of about 1 micron toabout 125 microns, or more specifically about 3 microns to about 95microns. In an exemplary embodiment, the boundary layer has a thicknessof about 20 microns or less, more specifically about 5 microns to about15 microns.

According to one aspect of the invention, a boundary layer of thedesired thickness is formed using solution or dispersion chemistry.Solution and dispersion chemistries are well known to those skilled inthe art. While the percentage solids will vary, in one embodiment, asolution or dispersion having about 10-15% solids was found to be usefulfor formation of the boundary layer.

In one embodiment, a polyurethane film suitable for the boundary layercan be prepared and formed into a film using solution or dispersionchemistry and film coating techniques known to those skilled in the art.Such a film can be prepared by reacting components, including at leastone isocyanate-reactive component, at least one isocyanate-functionalcomponent, and, optionally, at least one reactive emulsifying compound,to form an isocyanate-terminated polyurethane prepolymer. Thepolyurethane prepolymer can then be dispersed, and optionallychain-extended, in a dispersing medium to form a polyurethane-baseddispersion that can be cast to form a polyurethane film. This method ispreferred for preparation of boundary layers according to the invention.

When the polyurethane film is prepared from an organic solventborne orwaterborne system, once the solution or dispersion is formed, it iseasily applied to a substrate and then dried to form a polyurethanefilm. As known to those of ordinary skill in the art, drying can becarried out either at room temperature (i.e., about 20° C.) or atelevated temperatures (e.g., about 25° C. to about 150° C.). Forexample, drying can optionally include using forced air or a vacuum.This includes the drying of static-coated substrates in ovens, such asforced air and vacuum ovens, or drying of coated substrates that arecontinuously conveyed through chambers heated by forced air,high-intensity lamps, and the like. Drying may also be performed atreduced (i.e., less than ambient) pressure.

Any suitable isocyanate-reactive component can be used. Theisocyanate-reactive component contains at least one isocyanate-reactivematerial or mixtures thereof. As understood by one of ordinary skill inthe art, an isocyanate-reactive material includes at least one activehydrogen. Those of ordinary skill in the polyurethane chemistry art willunderstand that a wide variety of materials are suitable for thiscomponent. For example, amines, thiols, and polyols areisocyanate-reactive materials.

However, it is preferred that the isocyanate-reactive material be ahydroxy-functional material. Polyols are the preferredhydroxy-functional material used in the present invention. Polyolsprovide urethane linkages when reacted with an isocyanate-functionalcomponent, such as a polyisocyanate.

Polyols, as opposed to monols, have at least two hydroxy-functionalgroups. Diols contribute to formation of relatively high molecularweight polymers without requiring crosslinking, such as isconventionally introduced by polyols having greater than twohydroxy-functional groups. Examples of polyols useful in the presentinvention include, but are not limited to, polyester polyols (e.g.,lactone polyols) and the alkylene oxide (e.g., ethylene oxide;1,2-epoxypropane; 1,2-epoxybutane; 2,3-epoxybutane; isobutylene oxide;and epichlorohydrin) adducts thereof, polyether polyols (e.g.,polyoxyalkylene polyols, such as polypropylene oxide polyols,polyethylene oxide polyols, polypropylene oxide polyethylene oxidecopolymer polyols, and polyoxytetramethylene polyols;polyoxycycloalkylene polyols; polythioethers; and alkylene oxide adductsthereof), polyalkylene polyols, polycarbonate polyols, mixtures thereof,and copolymers therefrom.

Polycarbonate-based polyurethanes are preferred according to oneembodiment. It was found that this type of polyurethane chemistry easilyfacilitated obtainment of polyurethane-based films with propertiesdesired. Accordingly, in one preferred embodiment, a polycarbonate diolis used to prepare polycarbonate-based polyurethane according to theinvention. Although polyols containing more than two hydroxy-functionalgroups are generally less preferred than diols, certain higherfunctional polyols may also be used in the present invention. Thesehigher functional polyols may be used alone, or in combination withother isocyanate-reactive materials, for the isocyanate-reactivecomponent.

For broader formulation latitude, at least two isocyanate-reactivematerials, such as polyols, may be used for the isocyanate-reactivecomponent. However, as any suitable isocyanate-reactive component can beused to form the polyurethane, much latitude is provided in the overallpolyurethane chemistry.

The isocyanate-reactive component is reacted with anisocyanate-functional component during formation of the polyurethane.The isocyanate-functional component may contain oneisocyanate-functional material or mixtures thereof. Polyisocyanates,including derivatives thereof (e.g., ureas, biurets, allophanates,dimers and trimers of polyisocyanates, and mixtures thereof),(hereinafter collectively referred to as “polyisocyanates”) are thepreferred isocyanate-functional materials for the isocyanate-functionalcomponent. Polyisocyanates have at least two isocyanate-functionalgroups and provide urethane linkages when reacted with the preferredhydroxy-functional isocyanate-reactive components. In one embodiment,polyisocyanates useful for preparing polyurethanes are one or acombination of any of the aliphatic or aromatic polyisocyanates commonlyused to prepare polyurethanes.

Generally, diisocyanates are the preferred polyisocyanates. Usefuldiisocyanates include, but are not limited to, aromatic diisocyanates,aromatic-aliphatic diisocyanates, aliphatic diisocyanates,cycloaliphatic diisocyanates, and other compounds terminated by twoisocyanate-functional groups (e.g., the diurethane oftoluene-2,4-diisocyanate-terminated polypropylene oxide polyol).

Examples of preferred diisocyanates include the following: 2,6-toluenediisocyanate; 2,5-toluene diisocyanate; 2,4-toluene diisocyanate;phenylene diisocyanate; 5-chloro-2,4-toluene diisocyanate;1-chloromethyl-2,4-diisocyanato benzene; xylylene diisocyanate;tetramethyl-xylylene diisocyanate; 1,4-diisocyanatobutane;1,6-diisocyanatohexane; 1,12-diisocyanatododecane;2-methyl-1,5-diisocyanatopentane;methylenedicyclohexylene-4,4′-diisocyanate;3-isocyanatomethyl-3,5,5′-trimethylcyclohexyl isocyanate (isophoronediisocyanate); 2,2,4-trimethylhexyl diisocyanate;cyclohexylene-1,4-diisocyanate; hexamethylene-1,6-diisocyanate;tetramethylene-1,4-diisocyanate; cyclohexane-1,4-diisocyanate;naphthalene-1,5-diisocyanate; diphenylmethane-4,4′-diisocyanate;hexahydro xylylene diisocyanate; 1,4-benzene diisocyanate;3,3′-dimethoxy-4,4′-diphenyl diisocyanate; phenylene diisocyanate;isophorone diisocyanate; polymethylene polyphenyl isocyanate;4,4′-biphenylene diisocyanate;4-isocyanatocyclohexyl-4′-isocyanatophenyl methane; andp-isocyanatomethyl phenyl isocyanate.

When preparing polyurethane dispersions for casting into layers ofpolyurethane, the isocyanate-reactive and isocyanate-functionalcomponents may optionally be reacted with at least one reactiveemulsifying compound according to one embodiment of the invention. Thereactive emulsifying compound contains at least one anionic-functionalgroup, cationic-functional group, group that is capable of forming ananionic-functional group or cationic-functional group, or mixturesthereof. This compound acts as an internal emulsifier because itcontains at least one ionizable group. Thus, these compounds arereferred to as “reactive emulsifying compounds.”

Reactive emulsifying compounds are capable of reacting with at least oneof the isocyanate-reactive and isocyanate-functional components tobecome incorporated into the polyurethane. Thus, the reactiveemulsifying compound contains at least one, preferably at least two,isocyanate- or active hydrogen-reactive- (e.g., hydroxy-reactive)groups. Isocyanate- and hydroxy-reactive groups include, for example,isocyanate, hydroxyl, mercapto, and amine groups.

Preferably, the reactive emulsifying compound contains at least oneanionic-functional group or group that is capable of forming such agroup (i.e., an anion-forming group) when reacted with theisocyanate-reactive (e.g., polyol) and isocyanate-functional (e.g.,polyisocyanate) components. The anionic-functional or anion-forminggroups of the reactive emulsifying compound can be any suitable groupsthat contribute to ionization of the reactive emulsifying compound. Forexample, suitable groups include carboxylate, sulfate, sulfonate,phosphate, and similar groups. As an example, dimethylolpropionic acid(DMPA) is a useful reactive emulsifying compound. Furthermore,2,2-dimethylolbutyric acid, dihydroxymaleic acid, and sulfopolyesterdiol are other useful reactive emulsifying compounds. Those of ordinaryskill in the art will recognize that a wide variety of reactiveemulsifying compounds are useful in preparing polyurethanes for thepresent invention.

One or more chain extenders can also be used in preparing polyurethanesof the invention. For example, such chain extenders can be any or acombination of the aliphatic polyols, aliphatic polyamines, or aromaticpolyamines conventionally used to prepare polyurethanes.

Illustrative of aliphatic polyols useful as chain extenders include thefollowing: 1,4-butanediol; ethylene glycol; 1,6-hexanediol; glycerine;trimethylolpropane; pentaerythritol; 1,4-cyclohexane dimethanol; andphenyl diethanolamine. Also note that diols such as hydroquinonebis(β-hydroxyethyl)ether;tetrachlorohydroquinone-1,4-bis(β-hydroxyethyl)ether; andtetrachlorohydroquinone-1,4-bis(β-hydroxyethyl)sulfide, even though theycontain aromatic rings, are considered to be aliphatic polyols forpurposes of the invention. Aliphatic diols of 2-10 carbon atoms arepreferred. Especially preferred is 1,4-butanediol.

Illustrative of useful polyamines are one or a combination of thefollowing: p,p′-methylene dianiline and complexes thereof with alkalimetal chlorides, bromides, iodides, nitrites and nitrates;4,4′-methylene bis(2-chloroaniline); dichlorobenzidine; piperazine;2-methylpiperazine; oxydianiline; hydrazine; ethylenediamine;hexamethylenediamine; xylylenediamine; bis(p-aminocyclohexyl)methane;dimethyl ester of 4,4′-methylenedianthranilic acid; p-phenylenediamine;m-phenylenediamine; 4,4′-methylene bis(2-methoxyaniline); 4,4′-methylenebis(N-methylaniline); 2,4-toluenediamine; 2,6-toluenediamine; benzidine;3,4′-dimethylbenzidine; 3,3′-dimethoxybenzidine; dianisidine;1,3-propanediol bis(p-aminobenzoate); isophorone diamine;1,2-bis(2′-aminophenylthio)ethane; 3,5-diethyl toluene-2,4-diamine; and3,5-diethyl toluene-2,6-diamine. The amines preferred for use are4,4′-methylene bis(2-chloroaniline); 1,3-propanediolbis(p-aminobenzoate); and p,p′-methylenedianiline and complexes thereofwith alkali metal chlorides, bromides, iodides, nitrites and nitrates.

No matter the chemistry, the boundary layer is preferably essentiallyuncrosslinked. While the use of certain amounts of crosslinker may stillallow formation of a suitable boundary layer, if crosslinkers arepresent, they are generally used in an amount of less than about 4 partsby weight, and preferably less than about 2 parts by weight, based on100 parts by weight of any polymer crosslinkable therewith prior to anycrosslinking reaction. Further, crosslinkers may be present if they arenot used in combination with polymers that are crosslinkable therewithor where, if crosslinkable, resulting crosslink density is minimal(e.g., due to minimal reactive sites on the base polymer) so as not tosignificantly affect stretchability of the overall multi-layer film. Ina preferred embodiment, the boundary layer is essentially free ofcrosslinkers and reaction products thereof. As such, crosslinkers andreaction products are not discernible when using chemical analysis.

In an exemplary preferred embodiment, a polyurethane-based topcoat layerdescribed in U.S. Patent Publication No. US-2008-0286576, incorporatedherein by reference in its entirety, is used as the boundary layer. Sucha layer is described in U.S. Patent Publication No. US-2008-0286576 asan exterior (or topcoat) layer applied to a carrier layer in order toimpart improved gloss retention. Unexpectedly, use of such a materialinstead as a boundary layer within (and interior to) a multi-layer filmfacilitates obtainment of superior stretchability of the multi-layerfilm without compromised integrity and while allowing broaderformulation latitude in the topcoat layer to obtain properties desiredtherein. Compromised integrity is evidenced by, for example, cracking,splitting, and the like of the multi-layer film upon stretching.

Adhesive Layer

The adhesive layer is outwardly exposed on a major planar side of themulti-layer film opposite from that on which the topcoat layer ispresent. Any suitable adhesive can be used for the adhesive layeraccording to the invention. In a preferred embodiment, the adhesivelayer comprises a pressure-sensitive adhesive.

While any suitable chemistry can be used for the base polymer in theadhesive layer, (meth)acrylate—acrylate and methacrylate—chemistry ispreferred. However, other suitable chemistries are known to thoseskilled in the art and include, for example, those based on syntheticand natural rubbers, polybutadiene and copolymers thereof, polyisopreneor copolymers thereof, and silicones (e.g., polydimethylsiloxane andpolymethylphenylsiloxane). Any suitable additives can be present inconjunction with the base polymer in the adhesive layer.

In particular, an adhesive based on 2-ethyl hexyl acrylate, vinylacetate, and acrylic acid monomers polymerized as known to those skilledin the art was found useful in one embodiment of the invention. Theadhesive can be crosslinked, for example, using conventional aluminum ormelamine crosslinkers.

In one embodiment, the adhesive layer has a thickness of about 5 micronsto about 150 microns. In a further embodiment, the adhesive layer has athickness of about 30 microns to about 100 microns. However, thethickness of the adhesive layer can vary substantially without departingfrom the spirit and scope of the invention.

Similar to temporary use of a liner on the topcoat layer, until itsapplication on a surface, the adhesive layer can be protected using, forexample, a conventional release liner. As such, the multi-layer film canbe stored and shipped easily in roll or other forms until itsapplication.

Formation of Multi-Layer Film

In one embodiment, each of the individual layers of the multi-layer filmis prepared before assembly into the final multi-layer film. Anysuitable method for preparation of each can be used as known to thoseskilled in the art.

For preparation of the carrier layer, for example, a film can beextruded onto a separate carrier film (e.g., polyester film) to form asupported carrier layer, after which the boundary layer is formedthereon. The supporting carrier film is removed at some point before theadhesive layer is applied to the side of the carrier layer opposite theboundary layer.

For preparation of the adhesive layer, any suitable method can be used.For example, a film of the desired thickness can be cast onto a releasefilm according to one embodiment and as known to those skilled in theart. In one embodiment, the film of adhesive contained on the releasefilm can be laminated to the carrier layer after the supporting carrierfilm is removed from the carrier layer.

For preparation of the topcoat layer, any suitable method can be used.For example, a topcoat film of the desired thickness can be cast onto asmooth film (e.g., polyester) according to one embodiment and as knownto those skilled in the art. In one embodiment, the supported topcoatfilm is then laminated to the boundary layer. The smooth film used forformation of the topcoat film can remain in the assembly untilapplication of the sheet to a surface in order to provide extraprotection during shipping and storage of the multi-layer film.According to this embodiment, any suitable method can be used tolaminate the topcoat layer to the boundary layer. According to anotherembodiment, the topcoat layer is formed by direct coating onto theboundary layer according to conventional methods.

While the above-described process relies primarily on preparation ofindividual layers and then adherence of those layers together to formthe multi-layer film, according to another embodiment of the invention,some of the layers can be formed simultaneously by co-extrusion.Individual layers may be in-situ polymerized into a film format asdescribed in, for example, U.S. Pat. No. 8,828,303, U.S. PatentPublication No. US-2011-0137006-A1, and PCT Patent Application No. WO2017/156507. No matter what method is used, the process can be acontinuous or batch process.

Use of Multi-Layer Film

Multi-layer films of the invention are useful in a range of indoor andoutdoor applications in, for example, the transportation, architecturaland sporting goods industries. The multi-layer films can advantageouslybe applied to at least a portion of a surface of any article whereprotection or decoration (e.g., with paint) is desired. Such articlesinclude, for example, motorized vehicles and non-motorized vehicles(e.g., conventional bicycles) amongst a multitude of other applications.Surfaces on which the multi-layer films are applicable can be, forexample, painted or unpainted. When the multi-layer film is pigmented orotherwise, it can be used itself as paint in film form (also referred toas a paint film applique). When the multi-layer film is adhered to asurface primarily for the purpose of protecting paint existing on theunderlying surface, it is often referred to as a paint protection film.

Multi-layer films of the invention can be readily and easily applied toa surface based on knowledge of those skilled in the art. The adhesivelayer is generally adhered to the surface to be protected after removalof any release liner present thereon to expose the adhesive. When apressure-sensitive adhesive layer is used, the multi-layer film can bemore easily repositioned before being firmly adhered to a surface. Afterapplication of the multi-layer film to a surface, if used, the temporaryliner adjacent the topcoat layer is removed to outwardly expose thetopcoat layer during use.

Exemplary embodiments and applications of the invention are described inthe following non-limiting examples.

Scanning Electron Micrography (SEM) Test Method

In order to evaluate properties associated with stretchability for eachof the exemplified multi-layer films, samples were prepared, stretched,and analyzed in high vacuum using SEM to determine the presence of anycracks, splitting, or the like. Specifications for the SEM imagesobtained using a FEI Quanta™ 200 SEM (Thermo Fisher Scientific ofHillsboro, Oreg.) were as follows: HV 30.0 kV, Spot 3.0, WD 11.8 mm,Magnification 100×, and Det. SSD.

Four film samples of each exemplified multi-layer film were applied to astainless steel test panel in an elongated state after being stretchedto the desired elongation percentage (all performed at roomtemperature). One of the film samples was longitudinally hand-stretchedby 30%, another of the film samples was longitudinally hand-stretched by40%, another of the film samples was longitudinally hand-stretched by50%, and the other film sample was longitudinally hand-stretched by 60%.It is to be understood that a film sample hand-stretched by 30% iselongated to 130% of its initial length. The same principle applies withrespect to indicated stretch percentages.

Approximately one hour after application of each film sample to the testpanel, the assembly was exposed to an elevated temperature of about 90°C. by placing the assembly into a box oven for either two or twenty-fourhours, as indicated below. After removal from the oven and cooling toroom temperature, the samples were analyzed using SEM.

Alternative Methods for Viewing Defects in Stretched Multi-Layer Films

As an alternative to removing a multi-layer film from a surface to whichit has been applied for analysis using the Scanning Electron MicroscopyTest Method herein, an applied film may be analyzed after itsapplication to a surface using an optical microscope, or even amagnifying glass, to determine presence of defects including crackswithin and splitting of the film. Many such defects are visible usingthese alternative methods.

Example 1

A web-polymerized polyurethane carrier layer having a thickness of5.7-mils was coated with 11 GSM of a polycarbonate polyurethane boundarylayer that was then topcoated with 5 GSM polyurethane topcoat. Theopposite side of the polyurethane carrier layer was coated with acrylicpressure sensitive adhesive to a thickness of 1.5 mils.

Samples were tested after exposure to the elevated temperature of about90° C. for two hours. Results of SEM analysis of the film are tabulatedin Table 1 and corresponding to the amount stretched. Photographs of theSEM images after the multi-layer film of Example 1 was stretched 30% and60% are respectively included as FIGS. 1A and 1B herein.

Comparative Example C1

A web-polymerized polyurethane carrier layer having a thickness of6-mils was topcoated with 11 GSM polyurethane topcoat. The opposite sideof the polyurethane carrier layer was coated with acrylic pressuresensitive adhesive to a thickness of 1.5 mils.

Samples were tested after exposure to the elevated temperature of about90° C. for two hours. Results of SEM analysis of the film are tabulatedin Table 1 and corresponding to the amount stretched. Photographs of theSEM images after the multi-layer film of Comparative Example C1 wasstretched 30% and 60% are respectively included as FIGS. 2A and 2Bherein. As illustrated in FIG. 2B, at least four substantiallytransverse cracks resulted after being stretched 60%.

Comparative Example C2

An extruded polyurethane carrier layer (extruded from material obtainedfrom Lubrizol under the Estane® ALR CL93A-V trade designation) having athickness of 6-mils was topcoated with 11 GSM polyurethane topcoat. Theopposite side of the polyurethane carrier layer was coated with acrylicpressure sensitive adhesive to a thickness of 1.5 mils.

Samples were tested after exposure to the elevated temperature of about90° C. for two hours. Results of SEM analysis of the film are tabulatedin Table 1 and corresponding to the amount stretched. Photographs of theSEM images after the multi-layer film of Comparative Example C2 wasstretched 30% and 60% are respectively included as FIGS. 3A and 3Bherein. As illustrated in FIG. 3B, at least four large, substantiallytransverse cracks resulted after being stretched 60%.

TABLE 1 Film Amount Stretched Example 30% 40% 50% 60% 1 OK OK OK OK C1OK OK Cracking Cracking C2 OK Cracking Cracking Cracking

As illustrated in Table 1, when stretched by 30%, none of the filmexamples exhibited compromised properties. Upon stretching further,however, the film sample of Comparative Example C2 cracked each time.The film sample of Example 1 remained uncompromised even when stretchedby 60%. Upon stretching of 50% or 60%, the film sample of ComparativeExample C1 cracked.

Comparative Example C3

SunTek® PPF ULTRA paint protection film commercially available fromEastman Chemical Company (Martinsville, Va.) was analyzed. Samples weretested after exposure to the elevated temperature of about 90° C. fortwo hours. Photographs of the SEM images after the multi-layer film ofComparative Example C3 was stretched 30% and 60% are respectivelyincluded as FIGS. 4A and 4B herein. As illustrated in FIG. 4B, at leastfour large, substantially transverse cracks resulted after beingstretched 60%.

Example 2

A multi-layer film was prepared according to Example 1. Before testing,however, samples were exposed to the elevated temperature of about 90°C. for the extended period of twenty-four hours. Results of SEM analysisof the film are tabulated in Table 2 and corresponding to the amountstretched.

Comparative Example C4

A multi-layer film was prepared according to Comparative Example C1.Before testing, however, samples were exposed to the elevatedtemperature of about 90° C. for the extended period of twenty-fourhours. Results of SEM analysis of the film are tabulated in Table 2 andcorresponding to the amount stretched.

Comparative Example C5

A multi-layer film was prepared according to Comparative Example C2.Before testing, however, samples were exposed to the elevatedtemperature of about 90° C. for the extended period of twenty-fourhours. Results of SEM analysis of the film are tabulated in Table 2 andcorresponding to the amount stretched.

TABLE 2 Film Amount Stretched Example 30% 40% 50% 60% 2 OK OK OKCracking C4 OK Cracking Cracking Cracking C5 Cracking Cracking CrackingCracking

As illustrated in Table 1, when stretched by 30%, none of the filmexamples exhibited compromised properties. Upon stretching further,however, the film sample of Comparative Example C5 cracked each time.The film sample of Example 1 remained uncompromised even when stretchedby 60%. Upon stretching of 50% or 60%, the film sample of ComparativeExample C4 split.

Various modifications and alterations of the invention will becomeapparent to those skilled in the art without departing from the spiritand scope of the invention, which is defined by the accompanying claims.It should be noted that steps recited in any method claims below do notnecessarily need to be performed in the order that they are recitedunless expressly stated otherwise. Those of ordinary skill in the artwill recognize variations in performing the steps from the order inwhich they are recited. In addition, the lack of mention or discussionof a feature, step, or component provides the basis for claims where theabsent feature or component is excluded by way of a proviso or similarclaim language.

Further, as used throughout, ranges may be used as shorthand fordescribing each and every value that is within the range. Any valuewithin the range can be selected as the terminus of the range.Similarly, any discrete value within the range can be selected as theminimum or maximum value recited in describing and claiming features ofthe invention.

In addition, as discussed herein it is again noted that the compositiondescribed herein may comprise all components in one or multiple parts.Further, while reference is made herein to preparation of the variousintermediate components (e.g., prepolymers) recognize that some suchintermediate components may be commercially available and, as such, canbe used according to the invention as an alternative to otherwisepreparing the same. Other variations are recognizable to those ofordinary skill in the art. Note also that any molecular weights givenherein are number average molecular weights unless specified otherwise.Further, any properties described or measured herein are those existingat room temperature and atmospheric pressure unless specified otherwise.

1. A multi-layer film comprising sequential layers as follows: a topcoatlayer; a boundary layer, wherein the boundary layer promotesstretchability of the multi-layer film; a carrier layer; and an adhesivelayer.
 2. The multi-layer film of claim 1, wherein the film ispolyurethane-based.
 3. The multi-layer film of claim 1, wherein theadhesive layer comprises a pressure-sensitive adhesive.
 4. Themulti-layer film of claim 1, further comprising a release film on anexterior surface of the adhesive layer.
 5. The multi-layer film of claim1, further comprising a carrier film on an exterior surface of thetopcoat layer.
 6. The multi-layer film of claim 1, wherein the carrierlayer is in-situ polymerized.
 7. The multi-layer film of claim 1,wherein after exposure to a temperature of about 90° C. for two hoursand longitudinal stretching of the film by 40%, no visible cracks wereobserved or splitting of the film resulted, as evidenced by viewing ofthe film using the Scanning Electron Micrography Test Method herein. 8.The multi-layer film of claim 1, wherein after exposure to a temperatureof about 90° C. for two hours and longitudinal stretching of the film by60%, no visible cracks were observed or splitting of the film resulted,as evidenced by viewing of the film using the Scanning ElectronMicrography Test Method herein.
 9. The multi-layer film of claim 1,wherein after exposure to a temperature of about 90° C. for twenty-fourhours and longitudinal stretching of the film by 40%, no visible crackswere observed or splitting of the film resulted, as evidenced by viewingof the film using the Scanning Electron Micrography Test Method herein.10. The multi-layer film of claim 1, wherein after exposure to atemperature of about 90° C. for twenty-four hours and longitudinalstretching of the film by 60%, no visible cracks were observed orsplitting of the film resulted, as evidenced by viewing of the filmusing the Scanning Electron Micrography Test Method herein.
 11. Amulti-layer film comprising sequential layers as follows: a topcoatlayer; a boundary layer; a carrier layer; and an adhesive layer, whereinM10 modulus of the boundary layer is at least about 20% greater than M10modulus of the carrier layer.
 12. The multi-layer film of claim 11,wherein M10 modulus of the boundary layer is at least about 20% greaterthan M10 modulus of the topcoat layer sandwiching the boundary layer.13. The multi-layer film of claim 11, wherein M10 modulus of theboundary layer is at least about 50% greater than M10 modulus of thecarrier layer.
 14. The multi-layer film of claim 13, wherein M10 modulusof the boundary layer is at least about 50% greater than M10 modulus ofthe topcoat layer sandwiching the boundary layer.
 15. The multi-layerfilm of claim 11, wherein M10 modulus of the boundary layer is at leastabout 75% greater than M10 modulus of the carrier layer.
 16. Themulti-layer film of claim 15, wherein M10 modulus of the boundary layeris at least about 75% greater than M10 modulus of the topcoat layersandwiching the boundary layer.
 17. The multi-layer film of claim 11,wherein M10 modulus of the boundary layer is at least about 100% greaterthan M10 modulus of the carrier layer.
 18. The multi-layer film of claim17, wherein M10 modulus of the boundary layer is at least about 100%greater than M10 modulus of the topcoat layer sandwiching the boundarylayer.
 19. A multi-layer film comprising sequential layers as follows: atopcoat layer; a boundary layer; a carrier layer; and an adhesive layer,wherein the boundary layer has an ultimate elongation that is greaterthan ultimate elongation of the topcoat layer.
 20. The multi-layer filmof claim 19, wherein ultimate elongation of the boundary layer is atleast about 25% greater than ultimate elongation of the topcoat layer.21. The multi-layer film of claim 19, wherein ultimate elongation of theboundary layer is at least about 50% greater than ultimate elongation ofthe topcoat layer.
 22. The multi-layer film of claim 19, whereinultimate elongation of the boundary layer is at least about 100% greaterthan ultimate elongation of the topcoat layer.
 23. A multi-layer filmcomprising sequential layers as follows: a topcoat layer; a boundarylayer; a carrier layer; and an adhesive layer, wherein M10 modulus ofthe carrier layer is less than about 20 MPa at 25° C.
 24. Themulti-layer film of claim 23, wherein M10 modulus of the carrier layeris less than about 15 MPa at 25° C.
 25. The multi-layer film of claim23, wherein M100 modulus of the carrier layer is less than about 5 MPaat 25° C.
 26. The multi-layer film of claim 23, wherein M100 modulus ofthe carrier layer is less than about 4 MPa at 25° C.
 27. A multi-layerfilm comprising sequential layers as follows: a topcoat layer; aboundary layer; a carrier layer; and an adhesive layer, wherein M100modulus of the boundary layer at 60° C. is at least about 60% of M100modulus of that boundary layer at 25° C.
 28. The multi-layer film ofclaim 27, wherein M100 modulus of the boundary layer at 60° C. is atleast about 70% of M100 modulus of that boundary layer at 25° C.
 29. Themulti-layer film of claim 1, wherein the boundary layer has a thicknessthat is less than about 50% of thickness of the carrier layer.
 30. Themulti-layer film of claim 1, wherein the boundary layer has a thicknessthat is less than about 20% of thickness of the carrier layer.
 31. Anarticle comprising at least one surface having on at least a portionthereof the multi-layer film of claim
 1. 32. The article of claim 31,wherein the article comprises a motorized vehicle.
 33. The article ofclaim 31, wherein no visible cracks were observed or splitting of themulti-layer film occurred, as evident upon viewing of the film of thearticle using the Scanning Electron Micrography Test Method herein. 34.A method of using the multi-layer film of claim 1 to cover a surface ona motorized vehicle, the method comprising: providing the multi-layerfilm of claim 1; and applying the multi-layer film to the surface of themotorized vehicle.
 35. The method of claim 34, wherein the surface is atleast partially painted.
 36. The method of claim 34, wherein themulti-layer film comprises paint in film form.
 37. The method of claim34, wherein the multi-layer film is heated and stretched to conform tothe surface.
 38. The method of claim 34, wherein the surface isnon-planar.
 39. The method of claim 34, wherein no visible cracks wereobserved or splitting of the multi-layer film occurred as a result ofthe application, as evident upon viewing of the film after applicationof the film to the surface of the motorized vehicle.
 40. A method offorming the multi-layer film of claim 1, the method comprising a step ofin-situ polymerizing the carrier layer.